Limit switches are typically designed for use on machines with removal of a key bringing the machine to an immediate safe (de-energized) condition. Such switches provide enhanced operator safety when added to hinged or sliding guard doors, screens, or protective covers for enclosures. Such limit switches are typically well suited for industrial applications to cause the de-energizing of equipment in a manufacturing plant. Generally, such limit switches need to be constructed using heavy duty materials and methods to ensure their reliable operation in typically harsh manufacturing environments.
One typical difficulty with such limit switches is that keys can inadvertently be repositioned within the limit switch or altogether dislodged from the limit switch, causing an unexpected deactivation of the machinery. Such events are typically are the result of machinery vibrations causing motion of the key or by keys inadvertently catching on operator clothing or other moving objects. In some cases wear or misalignment of machinery, key, or switch components can increase the likelihood of such events. Therefore, there exists a need for limit switches which are resistant to inadvertent repositioning or dislodgement of keys.